JPS6155480B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dampening water composition for lithographic printing, and more particularly, to a lithographic printing method in which dampening water and ink are supplied to the plate surface of a plate cylinder using the same roller. The present invention relates to a dampening solution composition that is preferably used.

Lithographic printing is a printing method in which printing is performed using a printing plate that has an oil-sensitive surface in areas corresponding to image areas and a hydrophilic surface in areas corresponding to non-image areas. That is, ink is attached to the oil-sensitive surface, dampening water is attached to the hydrophilic surface, and printing is performed by utilizing the mutually repellent properties of ink and water. However, the ink and dampening water must be supplied to the printing plate in an appropriate balance. Applying too much dampening water will cause the ink to emulsify and cause dark colors.
Delayed drying can cause show-through, while too little dampening water can cause ink to adhere to non-image areas, causing stains.

At present, there are two common dampening water supply systems: the conventional method (hereinafter simply referred to as the "conventional method"), which supplies dampening water to the printing plate using a system separate from the ink supply; There is a simultaneous supply method (hereinafter simply referred to as "simultaneous supply method") in which water and water are given at the same time. The latter simultaneous supply method is described, for example, in Japanese Patent Publications No. 14341-14341 and Special Publication No. 14341 of 1973
- Described in Publication No. 8005.

This simultaneous supply method uses the same formation roller to supply ink and dampening water to the plate surface in lithographic printing, so it has the advantages of easy water volume adjustment and fewer sheets to be printed. If the conventional dampening water is used as is, water stains and plate stains will occur, making normal printing impossible.

BACKGROUND ART Conventionally, conventional dampening water has been made by adding phosphoric acid, gum arabic, etc. to water. For the reason mentioned above, in the case of the simultaneous supply method, it is necessary to further add alcohol such as isopropyl alcohol to the dampening water used in the conventional method. Approximately 25~
Printing is done with the addition of 20% by weight of inpropyl alcohol.

In this way, with the simultaneous supply method, it is possible to obtain normal printed matter only when using a dampening solution that is a mixture of about 25 to 20% by weight of alcohol, mainly inpropyl alcohol, in the dampening solution used in the conventional method. However, since the use of alcohol impairs the health of printing workers, there are regulations to prevent organic solvent poisoning (5% by weight or less in an aqueous solution), recommended concentration levels for the workplace environment (400ppm or less in the atmosphere), and there are also restrictions on flammability. It is regulated by the Fire Service Act to prevent the risk of fire caused by fire, and cannot be used in large quantities. For this reason, although the simultaneous supply method has an excellent printing effect, its widespread use has been delayed due to the high alcohol concentration in the dampening water, which has become a problem.

As a result of various studies to improve these problems, the present inventor found that even if the amount of isopropyl alcohol added was reduced by adjusting the viscosity range using a water-soluble compound, there was no water stick stain or plate stain. Furthermore, the present invention was completed by discovering that it is possible to prevent ink from bleeding into the dampening solution.

That is, the gist of the present invention is a dampening water composition for lithographic printing whose viscosity range is adjusted to 1.2 to 5.0 centistokes (15° C.) using a water-soluble compound.

Hereinafter, the above-mentioned present invention will be explained in detail.

First, water-soluble compounds used in the present invention include, for example, polyvinyl alcohol, polyvinylpyrrolidone, polyacrylic acid, sodium polyacrylate, polyethylene glycol, polyethylene oxide, sodium alginate, Maypro Gum Britaits gum, Crystal gum, Gum tragacanth, Indarka or water-soluble cellulose ethers such as methylcellulose (degree of substitution 1.6 to 2.0), ethylcellulose (degree of substitution 1.5 or less), carboxymethylcellulose (degree of substitution 0.6 to 1.0), carboxyethylcellulose, oxyethylcellulose (hydroxyethylcellulose), aminoethylcellulose, cyanethylcellulose, and these Examples include water-soluble polymer compounds such as derivatives, and other water-soluble low-molecular compounds such as glycerin ethylene glycol and pentaerythritol. These can be used alone or in combination of two or more.

In the present invention, the viscosity of the dampening solution is adjusted to 1.2 to 5.0 centistokes (15° C.) using the water-soluble compound described above. Furthermore, in practical terms, it is preferable to temporarily put the dampening water in a concentrated state in consideration of the burden of transportation to a printing factory, so it is desirable that the resin described above be capable of being concentrated, that is, one that can maintain fluidity even in a concentrated state. As such,
Among water-soluble compounds, water-soluble cellulose ether is most suitable.

For example, when using carboxymethyl cellulose with an average molecular weight of 180,000 to 190,000, a solution viscosity of 1.8 centistokes (15° C.) can be obtained by dissolving 0.02% by weight in dampening water. This resin has fluidity even as a 1.0% solution and can be used as a concentrated stock solution.

The present invention was developed based on the research on the physical properties of alcohol-containing dampening water, which revealed that alcohol has a low interfacial tension and high viscosity with respect to water, so it has the function of increasing the wetting effect on the plate surface. It is what was done. In particular, in the simultaneous supply method, when the dampening water transfers over the surfaces of the rubber roll, metal roll, and ink roll and is uniformly supplied with a thin water film, the dampening water may not only wet the roll surface but also Internal stress, ie appropriate viscosity, is required to maintain its own water film.

The effect of the water-soluble cellulose ether in the present invention is that it can increase the viscosity of the dampening solution and adjust it to 1.2 to 5.0 centistokes, which is much higher than the viscosity range of conventional conventional dampening solutions (0.9 centistokes or less). It's all about what you can do. If the viscosity is higher than 5.0 centistokes, the tendency of the ink to emulsify will gradually increase, and if the viscosity is lower than 1.2 centistokes, the wetting effect will decrease and staining will occur, which is not desirable.

Next, in the present invention, all the acids used in ordinary dampening solutions can be used to adjust the pH. For example, organic compounds such as phosphoric acid, citric acid, and gluconic acid, inorganic compounds such as nitric acid, sulfuric acid, and dichromic acid, and sodium and ammonium salts of the above acids can be used.

Note that when the pH is lower than 3.0, the viscosity of the aqueous solution of the water-soluble compound decreases, and the effect decreases. Moreover, if the pH is higher than 7.0, the plate surface corrosion effect will be reduced, which is not desirable.

The above-described dampening water composition for lithographic printing of the present invention is not only preferably used in a simultaneous supply system, but also can be used in a conventional system. In addition, the dampening water composition for lithographic printing of the present invention is proposed in the patent application (1) of the same date by the same applicant, in which a dampening water supply device is brought into contact with a lipophilic elastic roller having a smooth surface. The oleophilic elastic roller is in contact with the plate surface of the plate cylinder, and the oleophilic elastic roller and the first roller of the ink supply device are connected to each other. The present invention can also be applied to a dampening water supply system in an offset printing press in which an oleophilic roller with a smooth surface is provided in contact with the ink forming roller, and this roller is rotated and oscillated.

As is clear from the above explanation, according to the present invention, the amount of alcohol added is reduced, and it exhibits printing suitability without water stick stains or plate stains, and also has printing effects such as preventing ink from bleeding into dampening water. is obtained.

Next, the present invention will be described in more detail with reference to Examples. In addition, in the following text, "parts" indicate "parts by weight."

Example 1 A trace amount of an antifoaming agent was mixed into an aqueous solution obtained by dissolving 2 parts of oxyethyl cellulose (average molecular weight 170,000, manufactured by Fuji Chemical Co., Ltd., A5000) in 98 parts of water to prepare a stock solution of dampening water. A dampening water composition for lithographic printing was prepared by mixing 5 parts of the stock solution, 85 parts of water, and 10 parts of inpropyl alcohol. The viscosity was 2.0 centistokes as measured at 15°C using an Utsbelohde viscometer.
A printing test was conducted using an offset printing machine (Diamond 4-color machine manufactured by Mitsubishi Heavy Industries, Ltd.) equipped with a simultaneous supply device for ink and dampening water (manufactured by Dahlgren), and printed matter without water stick stains or plate stains was obtained. . In addition, the resistance to ink bleeding due to dampening water has been improved, resulting in special ink (Morohoshi Ink Co., Ltd., News Ink No. 10 Pink),
It was also confirmed that UV-curable ink (manufactured by the same company, UV Shear-in CAR-P) is also highly effective. The printing plate is manufactured by Fuji Photo Film Co., Ltd.
PS version (GAP) was used.

Example 2 An aqueous solution obtained by dissolving 1 part of sodium alginate (algin manufactured by Kimitsu Chemical Industry Co., Ltd.) in 99 parts of water was used as a stock solution in damp water. A dampening water composition for lithographic printing was obtained by mixing 1 part of the stock solution, 89 parts of water, and 10 parts of isopropyl alcohol. The viscosity was 1.8 centistokes. A printing test similar to that in Example 1 was conducted and similar results were obtained.

Example 3 Polyacrylic acid (Dyurimer AC manufactured by Nippon Pure Chemical Industries, Ltd.)
-20L) 1 part, polyethylene glycol #60001
1 part of phosphoric acid was added to an aqueous solution obtained by dissolving 1 part of phosphoric acid in 96 parts of water.
A dampening solution was prepared by mixing 0.5 parts of ammonium phosphate and 0.5 parts of citric acid, and adding a small amount of silicone emulsion type antifoaming agent (KM-73, manufactured by Shin-Etsu Chemical Co., Ltd.). A dampening water composition for lithography was prepared by mixing 2 parts of the stock solution with 93 parts of water and 5 parts of isopropyl alcohol. The viscosity was 2.2 cetistokes (15°C) and the pH was 4.7.

A printing test similar to that in Example 1 was conducted and similar results were obtained.

A printing test was conducted by further reducing the composition ratio of isopropyl alcohol, and it was confirmed that good printed matter could be obtained with a composition ratio of 5% or less.

Example 4 1 part of carboxymethyl cellulose (Celogen BSH-6 manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. with an average molecular weight of 180,000) was added to water.
0.5 parts of ammonium phosphate was mixed with 0.5 parts of ammonium phosphate in an aqueous solution obtained by dissolving 98 parts of the solution, and a trace amount of a silicone emulsion type antifoaming agent (KM-73, manufactured by Shin-Etsu Chemical Co., Ltd.) was mixed in to prepare a dampening water stock solution. A printing test similar to that in Example 3 was conducted and similar results were obtained.

Example 5 A printing test was conducted using the dampening solution of Example 1 on a conventional offset printing machine (Dia 4-color machine manufactured by Mitsubishi Heavy Industries, Ltd.), and as a result, good printed matter was obtained. Furthermore, there was an effect of reducing Molton stains. Furthermore, similar results were obtained with the dampening solutions of Examples 2, 3, and 4 using the conventional method.

Claims (1)

[Claims] 1. A lithographic printing dampening solution containing alcohol whose viscosity range is adjusted by adding a water-soluble compound.
1. A dampening water composition for lithographic printing, characterized in that the alcohol content is 1.2 to 5.0 centistokes (15° C.) and the alcohol content is 10% by weight or less. 2. The dampening water composition for lithographic printing according to claim 1, wherein the water-soluble compound is a water-soluble cellulose ether. 3. The dampening water composition for lithographic printing according to claim 1, which has a pH of 3.0 to 7.0 by adding an acid and a salt.